Process for recycling spent cathode materials

ABSTRACT

Systems and methods for direct recycling and upcycling of spent cathode materials using Flame-Assisted Spray Pyrolysis Technology (FAST). In illustrative embodiments, cathode layers are separated and collected from spent battery cells. The cathode laminate is ground to a powdered form and treated to remove contaminants by sifting into a hot stream of air which heats the powders, burning off contaminants. After cooling and particle collection, the powders may be dispersed into leaching solution to dissolve metal oxides and create an acid metal solution or ground into nano-sized primary particles and mixed with dispersing liquids to form a solution. The solution may be mixed with glycerol and additional metal salts to create a final precursor solution, which may undergo spray pyrolysis followed by drying and calcination to create cathode materials with high consistency and repeatability, or mixed with an alkaline metal salt solution and undergo electrodeposition to recover desired metal salts.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.63/144,646, filed Feb. 2, 2021, and is a Divisional application of U.S.patent application Ser. No. 17/591,476, filed on Feb. 2, 2022, thecontents of each of which are incorporated herein by reference in itsentirety, including but not limited to those portions that specificallyappear hereinafter.

TECHNICAL FIELD

This disclosure relates to systems, methods, and apparatus for therecycling of cathode materials for the manufacturing of batteries andcapacitors.

BACKGROUND

The various chemistries used in Li-ion cells results in variable backendvalue. Alternatively, unless they get recycled, Li-ion batteries (LIBs)could lead to a shortage of key materials (lithium, cobalt, and nickel)vital to the technology. Considering the fast growth of global demandsof LIBs, end-of-life (EOL) LIBs are most likely to become importantsecondary sources for various materials in the future. Finding ways todecrease the cost of recycling and recycling rate could thussignificantly reduce the life cycle cost of electric vehicle (EV)batteries, avoid material shortages, lessen the environmental impact ofnew material production, and potentially provide low-cost activematerials for new EV battery manufacturing. As one of the most promisingcathode materials in LIBs, layered oxides, such as LiNi_(x)Mn_(y)Co_(z),(NMC, x+y+z=1) (referred to as “NMC”) have been drawing much attentiondue to their high energy density for EV applications. Direct recyclingof NMC cathode materials is important to maintain domestic criticalmaterial reserves. Current cathode recycling processes includepyrometallurgy, hydrometallurgy and direct recycling. While each hasadvantages, these also have a number of disadvantages, including CO₂generation, relatively high energy consumption process cost orcomplexity, the recovery of alloys that require further processingthereby increasing total recycling costs, the inability to recover manyof the materials in LIBs, and others.

Similarly, conventional cathode materials synthesis includes aqueousco-precipitation, sol-gel, and solid-state synthesis (e.g., ballmill+high temperature calcination). Each of these processes has inherentproblems including multiple, slow, and energy-intensive steps, whichhinder high-throughput, direct battery material production.

A recycling process that was less resource and capital intensive, andsimpler and faster for cathode recycling would be an improvement in theart. Such a process that was capable of continuous feeding andproduction would be a further improvement in the art.

SUMMARY

The present disclosure is directed to systems and methods for the directrecycling of spent cathode materials using Flame-Assisted SprayPyrolysis Technology (FAST).

In one illustrative embodiment, cathode layers are separated andcollected from spent EV cells, such as from spent EV pouch cells in abattery assembly. The cathode laminate may be ground to a powdered formand treated to remove contaminants by sifting the powders into a hotstream of air which heats the powders, burning off all contaminants. Theresulting particles may then be cooled and collected.

In some embodiments, after particle collection the powders may bedispersed into leaching solution which works to dissolve metal oxides tocreate an acidic metal solution. The acidic metal solution may then bemixed with glycerol and additional metal acetates to create a finalprecursor solution.

In some other embodiments, after particle collection the powders may bedirected to a suitable mill, such as a jet-mill, or a series ofjet-mills. The mill(s) grind the spent secondary cathode powder intonano-sized primary particles in a continuous manner. In someembodiments, the particles may be mixed and/or coated with cathodeprecursors at different stages of jet-milling. Once jet-milling iscomplete, the produced nano-particles may then be collected andre-dispersed in a glycerol solution to create a final precursor solutionor suspension.

In some embodiments, the final precursor solution may then undergo spraypyrolysis by being pumped into the spray chamber along with compressedair, where it is dried and calcinated, creating cathode materials withhigh consistency and repeatability.

Spray pyrolysis may include the injection of the precursor solutioncontaining lithium source, metal salt and metal oxide particles insolvent at the top of a large spray chamber. A stream of hot air may besimultaneously heated and introduced to the system at the bottom of thespray chamber. A heat gradient is observed from the bottom of thechamber to the top, as the inlet air spirals vertically upward aroundthe walls, generically indicated by arrow 2205. Micro-droplets of theprecursor solution mix with the hot air at the inlet and reduce in sizeas excess solvent is evaporated, resulting in a micron-sized sphericaldry salt particle (in the case of leaching solution) or dry salt/metaloxide particle (in the case of jet-milling).

Continuous air flow will direct the dried particles produced in thespray drying zone to the bottom of the spray chamber, then through aflame heating zone to achieve final well calcined materials. Once theproduct particles have calcined to the desired crystal structure in theflame-Heating zone, air flow may push the products to a cooling zone,following which particle collection may take place.

In some other embodiments, the final precursor solution may instead bemixed with an alkaline solution to form an electrolyte forelectrochemical deposition of target metal salts. This can allow for theselective recovery of specific target metals.

DESCRIPTION OF THE DRAWINGS

It will be appreciated by those of ordinary skill in the art that thevarious drawings are for illustrative purposes only. The nature of thepresent disclosure, as well as other embodiments in accordance with thisdisclosure, may be more clearly understood by reference to the followingdetailed description, to the appended claims, and to the severaldrawings.

FIGS. 1A and 1B are process diagrams providing an overview of closedloop recycling processes in accordance with the principles of thepresent disclosure.

FIGS. 2A, 2B, and 2C are process diagrams providing overview of someillustrative cathode recycling system for conducting processes inaccordance with the principles of the present disclosure and FIG. 2Ddepicts a portion of the process diagram of FIG. 2C in more detail.

FIG. 3 depicts on illustrative arrangement of components for a cathoderegeneration system that may be used with the systems of FIGS. 2A, 2B,and 2C in a continuous processing line.

FIGS. 4A and 4B depict some illustrative chemical structures for theglycerol-based feedstocks for the precursor solutions useful in theprocesses in accordance with FIGS. 2A and 2B.

FIGS. 5A and 5B are process diagrams depicting stages of cathodematerial undergoing the spray pyrolysis processes depicted in FIGS. 2Aand 2B

FIG. 6 is a chart depicting a comparison of the processing times for theprocess in accordance with FIG. 2A and/or FIG. 2B to that of currentcathode recycling processes.

FIGS. 7A, 7B, and 7C are SEM images of spent cathode, separated spentcathode powder and recovered spent cathode powder after heat treatmentand FIG. 7D is a photograph of recovered spent cathode powder after heattreatment.

FIGS. 8A and 8B, respectively, are SEM images of secondary particles andprimary particles after jet-milling of spent cathode powder.

FIG. 9A is an SEM image of primary particles coated with relithiationagent and

FIG. 9B is a graph of the Raman spectra confirming successful coating ofrelithiation agent.

FIGS. 10A, 10B and 10C are SEM images of recycled secondary cathodeparticles taken at different magnifications, specifically 500×, 1000×and 4000×.

FIG. 11A is a comparison of the XRD spectra of jet milled and recycledcathode and FIG. 11B is a comparison of size distribution of jet milledand recycled cathode.

FIG. 12A is an SEM image of primary particles coated with upcyclingagents before calcination and FIG. 12B is an SEM image of primaryparticles coated with upcycling agent after calcination.

FIG. 13 is a chart showing the results of the cycling performance ofspent and recycled cathode with different calcination times.

FIG. 14 is a chart comparing the resulting voltage profiles of recycledand upcycled cathodes.

DETAILED DESCRIPTION

The present disclosure relates to apparatus, systems, and methods forthe direct recycling of spent cathode materials for the manufacturing ofbatteries. It will be appreciated by those skilled in the art that theembodiments herein described, while illustrative, are not intended tolimit this disclosure or the scope of the appended claims. Those skilledin the art will also understand that various combinations ormodifications of the embodiments presented herein can be made withoutdeparting from the scope of this disclosure. All such alternateembodiments are within the scope of the present disclosure.

The various chemistries used in Li-ion cells results in variable backendvalue. Alternatively, unless they get recycled, Li-ion batteries (LIBs)could lead to a shortage of key materials (lithium, cobalt, and nickel)vital to the technology. Considering the fast growth of global demandsof LIBs, end-of-life (EOL) LIBs are most likely to become importantsecondary sources for various materials in the future. Finding ways todecrease the cost of recycling and recycling rate could thussignificantly reduce the life cycle cost of electric vehicle (EV)batteries, avoid material shortages, lessen the environmental impact ofnew material production, and potentially provide low-cost activematerials for new EV battery manufacturing. As one of the most promisingcathode materials in LIBs, layered oxides, such as LiNi_(x)Mn_(y)Co_(z),(NMC, x+y+z=1) (NMC) have been drawing much attention due to their highenergy density for EV applications. Direct recycling of NMC cathodematerials is important to maintain domestic critical material reserves.The Flame-Assisted Spray Pyrolysis Technology (FAST) approach inaccordance with the present disclosure is a closed-loop recyclingprocess to directly recycle NMC materials from spent cathode scraps.Different from industrial available hydrometallurgical recyclingprocesses, in which the recovered materials are meal oxides or raw metalalloys, the proposed closed-loop recycling process will produceindustrial-grade cathode material directly from recycling stream. Thistechnique eliminates the conventional calcination step resulting in atime/energy-effective process. In addition, such processes arerelatively “green” as they may employ spent cathode scraps, acetate acidand environmentally friendly biomass-derived glycerol-based precursors,which can eliminate the toxic gases released during the recyclingprocess. In comparison to current known processes, the FAST approachesin accordance with the present disclosure may result in relativelyshorter production process with a high throughput, sufficient to makeon-site recycling possible; may result in a recovered cathode materialhave equal or, in some instances, better electrochemical performancecompared with c ent commercial cathode material; and/or may berelatively easy to scale up for cathode material mass recycling at a lowcost.

Spray pyrolysis may include the injection of the precursor solutioncontaining lithium source, metal salt and metal oxide particles insolvent at the top of a large spray chamber. A stream of hot air may besimultaneously heated and introduced to the system at the bottom of thespray chamber. A heat gradient is observed from the bottom of thechamber to the top, as the inlet air spirals vertically upward aroundthe walls. Micro-droplets of the precursor solution mix with the hot airat the inlet and reduce in size as excess solvent is evaporated,resulting in a dry salt particle (in the case of leaching solution) or adry salt/metal oxide particle (in the case of jet-milling).

Continuous air flow may be used to direct the dried particles producedin the spray drying zone to the bottom of the spray chamber, thenthrough a flame heating zone to achieve final well calcined materials.Once the product particles have calcined to the desired crystalstructure in the flame-heating zone, air flow may push the products to acooling zone, following which particle collection may take place.

It is also noted that the in some embodiments, the relatively earlycrystallization in glycerolate formation at low temperatures cansignificantly improve the crystallinity of NMC diode and that sinceglycerol is itself a fuel, and its combustion can provide heat energyfor materials processing, which can reduce the calcination temperatureand time for less energy consumption.

Turning to FIGS. 1A and 1B, process diagram for two illustrativeembodiments of a closed loop recycling processes 10A and 10B inaccordance with the principles of the present disclosure. Like elementsin the two depicted processes are indicated using the same referencenumerals.

Beginning with spent EV pouch cells 102, the used cathode layers arecollected and separated. The cathode laminate may then be ground to apowdered form as salvage cathode 104. The salvaged cathode may then betreated to remove contaminants by sifting the powders into a hot streamof air which heats the powders, burning off contaminants includingbinder and carbon as shown in flame zone 106. The resulting particlesmay then be cooled and collected

As depicted in FIG. 1A, in some embodiments, after particle collectionthe powders may be dispersed into leaching solution which works todissolve metal oxides to create an acidic metal solution, as indicatedby the acid etching step 108A. The acidic metal solution may then bemixed with a suitable solvent and additional metal acetates to create afinal precursor solution. Suitable solvents may include glycerol.ethanol, isopropanol, water, or other alcohols. It will be appreciatedthat any solvent that may be used to retain the dissolved components insolution or suspension, as by hydrogen bonding, which is sufficientlyevaporateable in the subsequent steps discussed further herein may beused.

As depicted in FIG. 1B, in some other embodiments, after particlecollection the powders may be directed to a jet-mill, as indicated at108B. The jet mill grinds the spent secondary cathode powder intonano-sized primary particles which may then be collected andre-dispersed in a lithium-containing glycerol solution to create a finalprecursor solution. It will be appreciated that in some embodiments, thejet-mill may actually be a series of jet-mills or other types of millsacting in stages to grind and/or coat the powder in stages. In some suchembodiments, the particles may be mixed and/or coated with cathodeprecursors at different stages of jet-milling, which can allow“upcycling” of the materials. The jet mill(s) may operate in acontinuous manner. Once jet-milling is complete, the producednano-particles may then be collected and re-dispersed in a glycerolsolution to create a final precursor solution. It will be appreciatedthat in some embodiments, additional metal acetate may be added to theprecursor solution to adjust the stoichiometry of the cathode material.It will be appreciated that in additional to jet-mills, any mill thatcan provide adequate grinding and mixing at a suitable speed may beused.

It will be further appreciated that where the collected large sizeparticles may be jet milled to produce nanosized particles which arethen dispersed into a vat where it mixes with a suitable solvent, suchas glycerol and additional metal acetates to adjust the desiredstoichiometry to create a final glycerolate precursor may result in theformation of a homogeneous suspension for efficient spray pyrolysis.This formation of glycerolate precursors and nanosized NMC particlessignificantly reduces the lithiation/annealing time of post-spraypyrolysis. As discussed previously herein, suitable solvents may includeglycerol. ethanol, isopropanol, water, or other alcohols. It will beappreciated that any solvent that may be used to retain the dissolvedcomponents in solution or suspension, as by hydrogen bonding, which issufficiently evaporateable in the subsequent steps discussed furtherherein may be used

The final precursor solution may then undergo spray pyrolysis by beingpumped into the spray chamber along with compressed air, where it isdried and calcinated, as indicated at 112. This creates a final recycledcathode material 114 with high consistency and repeatability, which maythen be used for suitable purposes, including in EV pouch cells forbattery assemblies.

Turning to FIGS. 2A, 2B, and 2C, these respectively depict a processdiagrams providing overviews of some illustrative cathode recyclingsystems for conducting processes in accordance with the principles ofthe present disclosure. FIG. 2D depicts a portion of the process diagramof FIG. 2C in more detail and FIG. 3 depicts one illustrativearrangement of components for a cathode regeneration system for acontinuous processing line for conducting this process. It will beappreciated that other potential components and arrangements may be usedin different embodiments as may be advantageous for particularinstallations and facilities or for the processing of particular usedcathode materials. Some illustrative embodiments of processes inaccordance with the principles of the present disclosure will bediscussed with reference to these Figures for clarity, but isnon-limiting, and is for the purpose of understanding processes inaccordance with this disclosure. Other arrangements and variations forparticular applications may be used. For clarity, common elements willbe indicated with like reference numerals.

Spent Cathode Powder Recovery

In spent powder recovery, generally indicated at 200 begins with usedcathode material, as collected from battery assemblies. As depicted at2001, the cathode layer is first separated from the current collector.It will be appreciated that in the current collectors separated from thecathode laminate may include aluminum, copper, stainless steel, nickel,titanium, and other appropriate materials. The separation may bemechanical or chemical or both and such collected current collectors maybe recycled using other appropriate methods.

Some exemplary spent cathode materials may include lithium metal oxides(LiMO, M=Ni, Mn, Co, Al, Ti, Cu, Sn, Nb, W, Sb, Fe, Mg, any 3d-5dmetals, and/or various combinations thereof), where lithium-basedbattery cathode materials are recycled. Where other alkali metal cathodematerials are being treated, the spent cathode materials may includeother alkali metal oxides. It will be appreciated that any transitionmetal used in cathodes may be recovered though the processes inaccordance with the present disclosure, but for clarity in explanation,lithium is used as an exemplary metal in the discussed embodiments.

The collected cathode laminate 2003 is the pulverized, as by feedinginto a hopper which continuously feeds into a grinding device 2004, topulverize the cathode into a powdered form. At this point, the groundpowder of the recycled cathodes still contains many contaminants whichmay include carbon/graphite, various polymeric binders, and low levelsof solvents. These contaminants must be burned off in order to recoverpure oxide NMC cathode. This treatment may be performed by sifting thepowders into a hot stream of air, as indicated at 2005. The hot streamof air may be contained in stainless steel piping, similar to the hotzones used in the spray pyrolysis chamber as discussed further herein. Asuitable heat source, such as a large natural gas burner may be used toheat the air stream, which in turn heats the powders, burning off allcontaminants left in the materials. The product is then cooled asindicated at 2007, where cool air is introduced to the stream of hotgases to cool the products. The cooled products may then be collected,as by routing through a cyclone 2008 where the particles are collected.

The carbonaceous material that are burnt off may include: graphite,carbon black, hard carbon, flake graphite, etc. The burn-off conditionsfor particular carbonaceous materials may require varying temperature,duration, fuel source, and chamber pressure, which can be controlled forparticular applications.

Precursor Formulation

In FIG. 2A, leachate precursor formulation, generally indicated at 210A,follows the spent cathode recovery. After particle collection, thecollected powders are dispersed into leaching solution, where it may becontinuously mixed via mechanical stirrers. The leaching bath 2102 worksto dissolve metal oxides, leaving bare metal powders. Exemplary leachingsolutions may be acidic use water solvent solutions, including acetateacid, sulfuric acid, hydrochloride acid, alkaline: sodium hydroxide,lithium hydroxide, potassium hydroxide, other suitable acids andmixtures of suitable acids. The concentration is from 0-10 M, pH from0-12. The ratio among Li, M and proton (or hydroxide) can vary dependingon the particular materials processed and the quality of the finalproduct. The acidic metal solution is then continuously fed from theleaching bath into precursor bath 2104A where it mixes with a suitablesolvent, such as glycerol and additional metal acetates, to creating thefinal precursor solution which is ready for spray pyrolysis.

In FIG. 2B, continuous precursor formulation, generally indicated at210B, follows the spent cathode recovery. After particle collection, thepowders are be directed to a jet mill 2110. As depicted, a cyclonecollector may be used for particle collection although it will beappreciated that this can vary based on the particular installation andthat other appropriate collectors may be used in other embodiments.

As the recovered cathode powder is continuously blown into the jet mill2110, the micron-sized secondary particles collide with each other andbreak down into nano-sized primary particles at high speed undercompressed air. The nano-sized particles may then be fed and dispersedinto the precursor bath 2104B under mechanical stirring to form ahomogeneous solution. The precursor bath may contain lithium hydroxide(LiOH) as the lithium compensation precursor and glycerol as thechelating agent. The molar concentration of LiOH depends on the lithiumdeficiency in the spent cathode materials. For example, if the spent NMChas a stoichiometry of Li_(0.5)Ni_(0.6)Mn_(0.2)Co_(0.2)O₂, the molarratio between LiOH to NMC would be 0.55:1 in order to produce a fullstoichiometry cathode of Li_(1.05)Ni_(0.6)Mn_(0.2)Co_(0.2)O₂. it will beappreciated that in some embodiments, Additional transition metalacetates may be added to the precursor solution to adjust thestoichiometry of the cathode material (e.g., adding Ni acetate, Mnacetate, Co acetate adjust the ratio of x, y, z in LiNi_(x)Mn_(y)Co_(z),where x+y+z=1).

It will be appreciated that the diameter of milling chamber, volume ofthe milling chamber, gas pressure, gas flow rate, particle feed rate,starting particle size, final particle size, chamber temperature, andmilling time of the jet mill may be monitored and varied to achieve thedesired particle size. Further, in addition to lithium hydroxide otherpotential lithium compensation precursors may include lithium carbonate,lithium acetate, Li sulfate, and lithium nitrate, among others. Whereother alkaline metal cathodes are used, the precursor will be changedaccordingly. Suitable solvents may include water, ethanol, isopropanol,glycerol or combination of thereof depending on the target viscosity. Ina typical installation, this may occur at a temperature of from about25° C. to about 80° C.

The nano-sized particles may then be fed and dispersed into theprecursor bath 2104B under mechanical stirring to form a homogeneoussolution. The precursor bath may contain lithium hydroxide (LiOH) as thelithium compensation precursor and a suitable solvent, such as glycerol,as the chelating agent. The molar concentration of LiOH depends on thelithium deficiency in the spent cathode materials. For example, if thespent NMC has a stoichiometry of Li_(0.5)Ni_(0.6)Mn_(0.2)Co_(0.2)O₂, themolar ratio between LiOH to NMC would be 0.55:1 in order to produce afull stoichiometry cathode of Li_(1.05)Ni_(0.6)Mn_(0.2)Co_(0.2)O₂. itwill be appreciated that in some embodiments, Additional transitionmetal acetates may be added to the precursor solution to adjust thestoichiometry of the cathode material (e.g., adding Ni acetate, Mnacetate, Co acetate adjust the ratio of x, y, z in LiNi_(x)Mn_(y)Co_(z),where x+y+z=1).

It will be appreciated that the diameter of milling chamber, volume ofthe milling chamber, gas pressure, gas flow rate, particle feed rate,starting particle size, final particle size, chamber temperature, andmilling time of the jet mill may be monitored and varied to achieve thedesired particle size. It will be appreciated that in addition to jetmills any suitable mills, including roller mills, spinning mills, etc.may be used. Further, in addition to lithium hydroxide other potentiallithium compensation precursors may include lithium carbonate, lithiumacetate, Li sulfate, and lithium nitrate, among others. Where otheralkaline metal cathodes are used, the precursor will be changedaccordingly. Suitable solvents may include water, ethanol, isopropanol,glycerol or combination of thereof depending on the target viscosity. Ina typical installation, this may occur at a temperature of from about25° C. to about 80° C.

In FIGS. 2C and 2D, continuous precursor formulation using a series ofjet-mills, generally indicated at 210C, follows the spent cathoderecovery. After particle collection, the powders are to be directed to afirst jet mill 2110C. As depicted, a cyclone collector may be used forparticle collection although it will be appreciated that this can varybased on the particular installation and that other appropriatecollectors may be used in other embodiments.

As the recovered cathode powder is continuously blown into the jet mill2110, the micron-sized secondary particles collide with each other andbreak down into nano-sized primary particles at high speed undercompressed air. The nano-sized particles may then be fed into asubsequent jet-mill 2111C, where the particles may be mixed and coatedwith additional cathode precursors for recycling or upcycling. Somesuitable additional cathode precursors may include: lithium hydroxide,lithium carbonate, lithium acetate, Li sulfate, lithium nitrate. Ifother alkaline metal cathodes are used, these precursors will be changedaccordingly; nickel nitrate, acetate, hydroxide, carbonate, sulfate,chloride; cobalt nitrate, acetate, hydroxide, carbonate, sulfate,chloride; manganese nitrate, acetate, hydroxide, carbonate, sulfate,chloride; aluminum nitrate, acetate, hydroxide, carbonate, sulfate,chloride; magnesium nitrate, acetate, hydroxide, carbonate, sulfate,chloride; niobium nitrate, acetate, hydroxide, carbonate, sulfate,chloride; tungsten nitrate, acetate, hydroxide, carbonate, sulfate,chloride; or other transition metal nitrate, acetate, hydroxide,carbonate, sulfate, chloride, and mixtures thereof.

It will be appreciated that although two jet-mills are depicted in FIGS.2C and 2D, that in other embodiments different numbers of mills may beused to allow for the addition of different cathode precursors underdifferent conditions or ensuring milling to a particular size.

The coated nano-sized particles may then be fed and dispersed into theprecursor bath 2104C under mechanical stirring to form a homogeneoussolution/suspension. The precursor bath contains solvents that can forma homogeneous solution of the coated cathode powders. The molarconcentration of relithiation agent (e.g., LiOH) and upcycling agents(e.g. Ni, Mn, Al, Co acetate) depend the lithium deficiency in the spendcathode materials or target upcycled cathode performance (e.g. Nicontent, capacity). For recycling, for example, if the spent NMC has astoichiometry of Li_(0.5)Ni_(0.6)Mn_(0.2)Co_(0.2)O₂, the molar ratiobetween LiOH to NMC may be 0.55:1 in order to produce a fullstoichiometry cathode of Li_(1.05)Ni_(0.6)Mn_(0.2)Co_(0.2)O₂. Forupcycling, for example, if the target composition isLi_(1.05)Ni_(0.7)Mn_(0.1)Co_(0.2)Al_(0.03), a corresponding molar ratioof the Li, Ni, Mn, Co, Al precursors should be added to the adjust thestoichiometry of the spent cathode with lower Ni content (i.e., Ni<0.7).

Additional transition metal acetates may be added to the precursorsolution to adjust the stoichiometry of the cathode material (e.g.,adding Ni acetate, Mn acetate, Co acetate adjust the ratio of x, y, z inLiNi_(x)Mn_(y)Co_(z), where x+y+z=1).

It will be appreciated that the diameter of milling chamber, volume ofthe milling chamber, gas pressure, gas flow rate, particle feed rate,starting particle size, final particle size, chamber temperature, andmilling time of the jet mill may be monitored and varied to achieve thedesired particle size and desired coating thickness. Further, inaddition to lithium hydroxide other potential lithium compensationprecursors may include lithium hydroxide, lithium carbonate, lithiumacetate, Li sulfate, lithium nitrate, among others. Where other alkalinemetal cathodes are used, the precursor will be changed accordingly.Suitable solvents may include water, ethanol, glycerol, isopropanol, orcombinations of thereof depending on the target viscosity. In a typicalinstallation, this may occur at a temperature of from about 25° C. toabout 80° C.

A precursor solution created using processes in accordance with thepresent disclosure, including those depicted in FIGS. 2A through 2D, mayinclude water, ethanol, glycerol, isopropanol or combination thereof.The metal acetates may include cathode precursors: lithium metal oxides(LiMO, M=Ni, Mn, Co, Al, Ti, Cu, Sn, Nb, W, Sb, Fe, Mg, any 3d-5dmetals, and/or various combinations thereof).

The molar ratio of metal and glycerol can vary from 0-0.5. Viscosityalso depends on the concentration of metal in glycerol. The compensationof extra cathode precursors is used to achieve the designed cathodestoichiometry (e.g., to produce Li_(1.05)Ni_(0.6)Mn_(0.2)Co_(0.2)O₂, theconcentration of Li⁺, Ni²⁺, Mn²⁺, Co²⁺, in the precursor solution has tobe 1.05M, 0.6M, 0.2M, 0.2M, respectively. The concentration will bemonitored, as by using as in-situ ICP (inductive coupled plasma) deviceand can be adjusted as required to produce suitable precursor solution.

Cathode Regeneration from Precursor Solution.

Cathode direct synthesis, generally indicated at 220, may then beperformed on the final precursor solution. As indicated at 2202, thissolution may be pumped into the spray chamber along with compressed air,where it is dried, creating micron-sized spherical cathode precursorparticles. This may take place using Flame-Assisted Spray PyrolysisTechnology (FAST). In one illustrative embodiment, this may be performedin a spray chamber 2204, which may be similar to that depicted at 3204in FIG. 3 .

As indicated at 2202, the precursor solution composing dry saltparticles (in the case of leaching solution) or dry salt/metal oxideparticles (in the case of jet-milling) in solvent may be continuouslyinjected at the top of a large spray chamber. The delivery pressure ofthe air and precursor solution at the inlet to the spray chamber can bechanged to alter the droplet size of the atomized solution, effectingthe overall particle size of the final product. A stream of hot air maybe simultaneously in a separate heating chamber 22006 (3206 in FIG. 3 )and introduced to the system at the bottom of the spray chamber. A heatgradient is observed from the bottom of the spray chamber to the top, asthe inlet air spirals vertically upward around the walls. Micro-dropletsof the precursor solution mix with the hot air at the inlet and reducein size as excess solvent is evaporated, resulting in a dry saltparticle.

It will be appreciated that the stream of hot air may be heated to asuitable temperature for performing the required drying. In the depictedembodiment, the air may be heated to around 400° C. in the separateheating chamber prior to introduction at the bottom of the dryingchamber. As depicted, the separate heating chamber may receive fuel,such as natural gas and air from suitable sources, such as pressurizedtanks 2208 and 2210 to allow the temperature to be controlled and variedas needed. It will be appreciated that the drying conditions includingduration, temperature, and spray chamber pressure may be varied based onthe input to achieve the desired drying. Additionally, parameters of theprecursor solution introduction including flow rate, spray nozzlediameter (droplet size), chamber pressure, and chamber temperature maysimilarly be varied to achieve the desired dry salt particle size.

When treating precursor solution formed following leaching, the dryingprocess discussed herein achieves solvent, such as glycerol, evaporationand salt precipitation to produce dried salt particle. When treatingprecursor solution formed following jet-milling, the drying processachieves solvent, such as glycerol, evaporation and salt precipitationto produce dried salt/metal oxide particles.

Flame-Assisted Heating Zone

The dried particles produced in the spray drying zone are directed tothe bottom of the drying chamber, generally indicated as theFlame-Assisted Heating Zone 2212. As indicated at 3212 in FIG. 3 , thiszone may be constructed as a series of hotter pipes. This direction maytake place via continuous air flow from the drying chamber through theflame assisted heating zone.

In the depicted embodiments, internal oxygen-methane torches increasethe temperature, and the particles pass therethrough with sufficientresidence time in this second-stage heating zone to achieve final wellcalcined materials. The various parameters of the heating may becontrolled to obtain the desired final products. For example, heatintroduced by the torches along the length of the airstream can beadjusted to either reflect changes in air flow, or to increase ordecrease the temperature at each hot section. Regulation of the fuel andoxygen ratios, pressures, and flow rates will ultimately determine theamount of heat that is put into the system. Modular increases to thelength of the flame-heating zone may also optimize the dwell time toenable the continuous production product with the desired crystal phase.In the depicted embodiment, the temperature can be adjusted from about600° C. to about 1000° C., and a typical processing temperature may beabout 800° C.

As indicated at 502A in FIG. 5A and 502B in FIG. 5B, the flame zoneprocess performs densification/calcination on the dried salt particlesor dried salt/metal oxide particles to produce calcined particles.

Cooling Zone

Once the product particles have calcined to the desired crystalstructure in the Flame-Heating Zone, the products are passed into acooling zone, generally indicated at 2214. As indicated at 3214 in FIG.3 , this cooling zone be constructed as a continuation of the series ofpipes. This direction of particles may take place via continuous airflow from the flame assisted heating zone to the cooling zone. In thedepicted embodiment, cool air enters the system through inlet ventspositioned around cooling pipes immediately downstream of theflame-heating zone, cooling the airstream. In one embodiment, theairstream may be cooled to room temperature. It will be appreciated thatthe flow rate, chamber pressure, chamber temperature may all bemonitored, varied and controlled to obtain the desired final product. Asindicated at 503A in FIG. 5A and 503B in FIG. 5B, the cooling zoneprocess produced a suitable final article from the calcined particle.

Following, the cooling zone, the particle collection takes place, asindicated at 2216. In the depicted embodiment, this collection may beperformed by a series of cyclone collectors and filters to collect ahigh percentage of the particulates before exhausting clean air to theenvironment. As depicted in FIG. 3 , there may be two cyclone collectors3216 and 3218, although it will be appreciated that this can vary basedon the particular installation and that other appropriate collectors maybe used in other embodiments.

Processes in accordance with the present disclosure may be able toprovide advantages over the current cathode recycling procedures,including the substantial reduction of processing time and requiredenergy. FIG. 6 is a comparison of the normalized processing timerequired for hydrometallurgy with co-precipitation (Process A),hydrometallurgy SP (Process B), and a FAST recycling process inaccordance with the present disclosure, showing processes in accordancewith the present disclosure may be up to 90% faster than currentprocesses. Additionally, they may produce a higher quality regeneratedcathode material that is post-calcination free and ready for use withminimal or no further processing. Such processes may be easily scalableand more environmentally friendly than the current processes as well.

Element Recovery Via Electrochemical Process

Processes in accordance with the present disclosure also allow for therecovery of metal elements, in addition to the recycling and/orupcycling of cathode materials. In such processes, the spent cathodepowder recovery may be performed as discussed previously herein inconnection with FIGS. 2A through 2C, in order to recover pure oxide NMCcathode. This may include the collection, separation, grinding and heattreatment to burn off contaminants from the materials left in thematerials, followed by cooling and collection.

Leachate precursor formulation: After particle collection, the powdersmay be dispersed into a vat of leaching solution where it iscontinuously mixed via mechanical stirrers. The leaching solution mayuse water as a solvent. Depending on the particular materials to bedissolved, it may be an acidic solution (e.g., acetate acid, sulfuricacid, hydrochloride acid, etc.), or an alkaline solution (e.g., sodiumhydroxide, lithium hydroxide, potassium hydroxide, etc.). It will beappreciated that solutions having a wide range of concentration (from0-10 M) and pH (from 0-12) may be used so long as the solution willfunction to dissolve metal oxides to form a solution for electiveelectrochemical deposition of metal salts from the collected powder,which may include lithium metal oxides (LiMO, M=Ni, Mn, Co, Al, Ti, Cu,Sn, Nb, W, Sb, Fe, Mg, and any 3d-5d metals).

Selective Electrodeposition

The leachate solvent is then mixed with an alkaline solution to form asuitable electrolyte for electrochemical deposition of target metalsalts. Suitable metal salt solutions may be alkaline metal based saltsolutions, including lithium nitrate, acetate, hydroxide, carbonate,sulfate, chloride; or other alkaline metal salts which are dissolved inwater, ethanol, isopropanol or other suitable solvents. It will beappreciated that solutions having a wide range of concentration (from0-10 M) and pH (from 0-12) may be used so long as the solution willfunction as an electrolyte to allow electrodeposition of the metal salttherefrom.

The electrolyte may undergo an electrode deposition process where twoelectrodes with different polarities are used to collect the metal saltof interest from the electrolyte. Suitable electrodeposition equipmentand current that are compatible with the electrolyte and metal ofinterest may be used. The produced metal salt product may be: nickelnitrate, acetate, hydroxide, carbonate, sulfate, chloride; cobaltnitrate, acetate, hydroxide, carbonate, sulfate, chloride; manganesenitrate, acetate, hydroxide, carbonate, sulfate, chloride; aluminumnitrate, acetate, hydroxide, carbonate, sulfate, chloride; magnesiumnitrate, acetate, hydroxide, carbonate, sulfate, chloride; niobiumnitrate, acetate, hydroxide, carbonate, sulfate, chloride; tungstennitrate, acetate, hydroxide, carbonate, sulfate, chloride; or othertransition metal nitrate, acetate, hydroxide, carbonate, sulfate,chloride. It will be appreciated that the particular solvent and powdersselected allow the desired metal to be recovered.

EXPERIMENTAL EXAMPLES

Cathode Powder Preparation

Example 1: Spent Cathode Powder

Cathode laminate was retrieved from a spent battery, and then separatedfrom the Al current collector. The carbon and polymer contaminate withinthe cathode laminate were burned off by passing the laminate through aheated environment at temperature of 400° C. for 1-30 minutes. Theheat-treated powder was then cooled down to room temperature andcollected for electrode preparation.

Scanning electron microscopy (SEM) samples were prepared by placing thecollected cathode powders on a conductive stage. SEM images were takenwith a JOEL JCM-7000. FIGS. 7A, 7B, and 7C are SEM images of spentcathode, separated spent cathode powder and recovered spent cathodepowder after heat treatment, respectively, from Example 1. FIG. 7D is aphotograph of recovered spent cathode powder after heat treatment. Theseimages demonstrate the efficiency of heat treatment to burn offcontaminates from the cathode materials.

Example 2: Recycled Cathode Powder

Cathode laminate was retrieved from a spent battery, and then separatedfrom the Al current collector. The carbon and polymer contaminate withinthe cathode laminate were burned off by passing the laminate through aheated environment at temperature of 400° C. for 1-30 minutes. Theheat-treated powder was then cooled down and fed into a jet mill to mixwith Li-acetate. The uniform powder mixture was then dispersed in aprecursor bath under stirring and introduced to a spray drying system.The spray system had an air nozzle pressure of 30 psi and precursor flowrate of 114 ml/min. The air entering the drying chamber had atemperature of 400° C. via natural gas burners and was introduced to thesystem at the bottom of the drying chamber. Micro-droplets of theprecursor solution mixed with the hot air at the inlet and reduced insize as excess solvent was evaporated, resulting in dry particles coatedwith relithiation agent. The particles were then calcined for differenttimes (1 minutes-10-hours) in the flame-assisted heating zone attemperature of 650° C., and then cooled down to room temperature andcollected for electrode preparation.

Scanning electron microscopy (SEM) samples were prepared by placing thecollected cathode powders on a conductive stage. SEM images were takenwith a JOEL JCM-7000. FIGS. 8A and 8B, respectively, are SEM images ofsecondary particles and primary particles after jet-milling of spentcathode powder. These demonstrate the efficiency of jet-milling tobreakdown the secondary particles into primary particles with size inrange of nm.

Raman samples were prepared by placing collected cathode powder in asample holder. Raman spectra were acquired with a confocal opticalmicroscope (WiTec AlphaSNOM™) using a solid-state 532 nm excitationlaser, a 20× objective, and a 600 grooves per millimeter grating. Thelaser spot size is approximately 1 μm. Acquisition times for eachspectrum ranged from 30 s to 3 min.

FIG. 9A is an SEM image of primary particles coated with relithiationagent and FIG. 9B is a graph of the Raman spectra confirming successfulcoating of relithiation agent. These demonstrate the efficiency ofjet-milling to breakdown the secondary particles into primary particleswith size in range of nm and achieve uniform cathode coating.

FIGS. 10A, 10B and 10C are SEM images of recycled secondary cathodeparticles taken at different magnifications specifically 500×, 1000× and4000×. These demonstrate that the recycled particles have the desiredsize (>10 um) and shape (spherical).

X-ray diffraction (XRD) samples were prepared by placing collectedcathode powder in a sample holder. Scanning was performed on a Bruker D8with Cu Kα radiation operated at 40 kV and 15 mA. A comparison of theXRD spectra of jet milled and recycled cathode is depicted in FIG. 11A,which demonstrates that the cathode structure is restored afterrecycling.

Cathode size distribution was conducted on multi-frequency laserdiffraction analyzer (Beckman Coulter LS230). Samples were prepared bydispersing 50 mg of cathode powder in 1 ml IPA. The dispersion of eachsample was added dropwise into the instrument. The size distribution isan average of three acquisitions. A comparison of size distribution ofjet milled and recycled cathode is depicted in FIG. 11B and shows thatthe spray pyrolysis process has successfully increased the size ofrecycled particles by forming secondary particles with high tap density,which are beneficial for electrode processing.

Example 3: Upcycled Cathode Powder

Cathode laminate was retrieved from a spent battery, and then separatedfrom the Al current collector. The carbon and polymer contaminate withinthe cathode laminate were burned off by passing the laminate through aheated environment at temperature of 400° C. for 1-30 minutes. Theheat-treated powder was then cooled down naturally and fed into a firstjet mill to break down the particle size, then a second jet-mill to mixwith Li-acetate, Ni-acetate, Co-acetate, and Al-acetate. The uniformpowder mixture was then dispersed in a precursor bath under stirring andintroduced to a spray drying system. The spray system had an air nozzlepressure of 30 psi and precursor flow rate of 114 ml/min. The airentering the drying chamber had a temperature of 400° C. via natural gasburners and was introduced to the system at the bottom of the dryingchamber. Micro-droplets of the precursor solution mixed with the hot airat the inlet and reduced in size as excess solvent is evaporated,resulting in dry particles coated with upcycling agents. The particleswere then calcined for different durations (1 minutes-10-hours) in theflame-assisted heating zone at temperature of 650° C., and then cooleddown to room temperature and collected for electrode preparation.

Scanning electron microscopy (SEM) samples were prepared by placing thecollected cathode powders on a conductive stage. SEM images were takenwith a JOEL JCM-7000. FIG. 12A is an SEM image of primary particlescoated with upcycling agents before calcination and FIG. 12B is an SEMimage of primary particles coated with upcycling agent aftercalcination. These images show that the uniform coating upcycling agentoccurred after the second jet-milling, and the smooth surface depictedafter calcination indicates a successful upcycling of the materials.

Example 4: Determination of Metal Concentrations in Aqueous Solutions

To determine the stoichiometry of cathode, samples of cathode powderwere digested in freshly prepared in acid solution (3:1 v/v mixture of37% v/v HCl and 70% v/v HNO3) and diluted in ultrapure water.Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was conducted onan Agilent 8900 ICP-QQQ to determine metal concentrations in theresulting aqueous solutions. The table below shows the cathodestoichiometry at pristine, spent and recycled states.

Li Ni Mn Co Pristine NMC622 1.014 0.601 0.197 0.201 Spent NMC622 0.9520.609 0.191 0.199 Recycled NMC622 1.017 0.603 0.200 0.197

Example 5: Cycling Tests

Battery cells were prepared and tested using cathode powder prepared inaccordance with Examples 2 and 3 using the following protocol.

Step 1. Electrode Preparation

Cathode preparation: (1) a slurry composed of cathode powder, conductivecarbon, and binder (polyvinylidene fluoride) with a mass ratio of9.4:0.3:0.3 was mixed using a planetary centrifugal mixer. (2) Theslurry was casted on an Al foil current collector via Dr. blade. (3) Theelectrode was baked at 100° C. for 1 hour and then roll-pressed beforeovernight drying at 120° C. The mass loading of the cathode wascontrolled at ˜20 mg cm².

Step 2. The electrode was cut into a diameter of 14 mm disk.

Step 3. CR20320 type coin cells were assembled in an argon-filled glovebox using a polyethylene (PE) separator, a lithium counter electrode,and a LiPF₆-based carbonate electrolyte.

Step 4. The cells were rested in an Arbin cycler at 25° C. for 12 hoursbefore electrochemical testing.

Step 5. Cycling tests were carried out with 3 formation cycles at 0.1C(1C=100% depth of discharge in 1 hour) and continuous cycling at C/3between 2.7-4.2 V vs. Li^(+/0) or 2.7-4.4 V vs. Li^(+/0)

FIG. 13 is a chart showing the results of the cycling performance ofspent and recycled cathode with different calcination times. Asdepicted, it was found that the recycled cathode powder with 4 hourspost-calcination showed the best performance with >90% capacityretention over 60 cycles. The capacity utilization recycled cathode is˜20 mAh/g higher than the spent cathode.

FIG. 14 is a chart comparing the resulting voltage profiles of recycledand upcycled cathodes. As depicted, it was found that the upcycledcathode shows ˜25 mAh/g higher capacity than the recycled cathode withthe same 4.2 cut-off voltage. With 4.4 V cut-off, the upcycled materialcan deliver 205 mAh/g capacity, ˜50 mAh/g higher than the recycledcathode.

While this disclosure has been described using certain embodiments, itcan be further modified while keeping within its spirit and scope. Thisapplication is therefore intended to cover any variations, uses, oradaptations of the disclosure using its general principles. Thisapplication is intended to cover any and all such departures from thepresent disclosure as come within known or customary practices in theart to which it pertains, and which fall within the limits of theappended claims.

The invention claimed is:
 1. A process for recycling of spent cathode materials, the process comprising: obtaining cathode laminate from spent rechargeable batteries; grinding the cathode laminate to a powdered form to provide a powdered cathode laminate; sifting the powdered cathode laminate into a hot stream of air to burn off contaminants to provide a sifted powdered cathode laminate; directing the sifted powdered cathode laminate into at least a first jet mill which grinds the sifted powdered cathode laminate into nano-sized primary particles; mixing the nano-sized primary particles with a dispersing liquid to create a precursor solution; performing spray drying on the precursor solution to obtain dried metal salt and/or metal oxide particles; heat treating the dried metal salt/metal oxide particles to obtain calcined particles; and cooling the calcined particles to obtain cathode materials.
 2. The process according to claim 1, wherein mixing the nano-sized primary particles with a dispersing liquid to create a precursor solution comprises mixing the nano-sized primary particles with a dispersing liquid comprising glycerol, isopropanol, ethanol, or water.
 3. The process according to claim 1, wherein mixing the nano-sized primary particles with a dispersing liquid further comprises mixing a cathode precursor material with the dispersing liquid, the cathode precursor material comprising an alkaline metal salt of nitrate, acetate, hydroxide, carbonate, sulfate, or chloride and/or transition metal salt of nitrate, acetate, hydroxide, carbonate, sulfate, or chloride.
 4. The process according to claim 1, wherein spray drying comprises injecting the precursor solution into the top of a chamber with a heated air current that forms a heat gradient from a bottom of the chamber to a top of the chamber.
 5. The process according to claim 4, wherein heat treating the dried metal salt particles to obtain calcined particles comprises passing the particles through a heating zone having a temperature of from about 600° C. to about 1000° C. for a sufficient time to produce calcined crystalline particles.
 6. The process according to claim 1, wherein heat treating the dried metal salt particles to obtain calcined particles comprises passing the particles through a heating zone having a temperature of from about 600° C. to about 1000° C. for a sufficient time to produce calcined crystalline particles.
 7. A process for upcycling of spent cathode materials; the process comprising: obtaining cathode laminate from spent rechargeable batteries; grinding the cathode laminate to a powdered form to obtain powdered cathode laminate; sifting the powdered cathode laminate into a hot stream of air to burn off contaminants to obtain sifted powdered cathode laminate; directing the sifted powdered cathode laminate into a first mill which grinds the sifted powdered cathode laminate into nano-sized primary particles; directing the nano-sized primary particles into at least a second mill where the nano-sized primary particles are mixed with a cathode precursor material to form a coating of the cathode precursor material on the nano-sized primary particles; mixing the coated nano-sized primary particles into a dispersing liquid to form a precursor solution; performing spray drying on the precursor solution to obtain dried metal salt and/or metal oxide particles; heat treating the dried metal salt and/or metal oxide particles to obtain calcined particles; and cooling calcined particles to obtain useable cathode materials.
 8. The process according to claim 7, wherein mixing the coated nano-sized primary particles into a dispersing liquid to form a precursor solution further comprises mixing the coated nano-sized primary particles with a dispersing liquid comprising glycerol, isopropanol, ethanol, or water.
 9. The process according to claim 7, wherein spray drying comprises injecting the precursor solution into the top of a chamber with a heated air current that defines a heat gradient from a bottom of the chamber to a top of the chamber. 